Organic corrosion inhibitors for zinc pigment

A severe problem with waterborne paints containing zinc pigments is hydrogen corrosion of the zinc in the aqueous alkaline paint media. The subject of the present study is the examination of corrosion inhibition of the zinc pigment in aqueous alkaline media by different high and low molecular weight organic inhibitors compared with that given by potassium dichromate. Potassium dichromate inhibits this corrosion reaction moderately, but a 4.0 mmol addition in 100 mL of the corrodent (1.2 wt-%) is required. Heterocyclic compounds are very poor corrosion inhibitors and less effective than potassium dichromate. Certain polymers with low acid numbers and low molecular weights and one particular epoxy ester resin are more effective inhibitors than potassium dichromate. Thus, some non-toxic polymers or paint resins can be considered as possible substitutes for toxic potassium dichromate.